Abstract Fatigue fracture in pipelines is the major failure mode during the service of oil and gas pipeline transportation. Welded joints, as the weakest region of a line-pipe, should be paid more attention firstly. Due to the need to remove the weld reinforcement at the beginning and end of each part of the pipeline for connection, it is necessary to study the fatigue properties of the welded joints before and after the removal of the weld reinforcement. In this work, a model with different heat affected sub-zones in the finite element analysis (FEA) was conducted to explore the fatigue properties of the welded joints with and without weld reinforcement for a ferrite/bainite dual-phase X80 line-pipe. The results show that the initiation positions of fatigue cracks are significantly different, and the fatigue strength is increased by about 1.3 times after removing the weld reinforcement. The reasons for the change of the initiation position before and after the removal of the weld reinforcement are discussed in terms of the material properties of HAZ and the effect of weld reinforcement. At the same time, the influence range of stress concentration at the weld toe on the fatigue property of the X80 line-pipe was analyzed by the FEA.

中文翻译：

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X80焊管去除焊缝加强筋前后焊缝疲劳特性模拟

摘要 管道疲劳断裂是油气管道输送使用过程中的主要失效模式。焊接接头作为管线管最薄弱的部位，首先要引起重视。由于连接管道各部分的首尾焊缝钢筋需要拆除，因此有必要对焊缝加固拆除前后焊接接头的疲劳性能进行研究。在这项工作中，进行了有限元分析 (FEA) 中具有不同热影响子区的模型，以探索铁素体/贝氏体双相 X80 管线管有和无焊缝增强的焊接接头的疲劳性能。结果表明，疲劳裂纹的起始位置明显不同，疲劳强度提高了约1。去除焊缝加强筋后 3 次。从热影响区的材料特性和焊缝加固的效果两个方面讨论了焊缝加固拆除前后起爆位置变化的原因。同时，利用有限元分析法分析了焊趾应力集中对X80管线管疲劳性能的影响范围。